Purification and characterisation of antibacterial peptide-containing compound derived from palm kernel cake

Palm kernel cake (PKC), the most useful by-product resulted from palm kernel oil production. In this study, PKC-derived protein product was found suitable for use as an antimicrobial agent with potent antibacterial activity, particularly against Bacillus species, after enzymatic hydrolysis with alcalase. The hydrolysate was further purified by gel filtration chromatography. The purified fraction was found to have 14.63 ± 0.70% (w/w) protein, a molecular mass of 2.4 kDa and low hemolytic activity (<50% hemolysis of human erythrocytes at concentration of 1000 μg/ml). The presence of lysine and the major component lauric acid derivative, as indicated by electrospray ionisation-mass spectrometry (ESI-MS) direct infusion and nuclear magnetic resonance (NMR) spectroscopy, may have contributed to the antibacterial effect of purified PKC fraction. This study suggests that the antibacterial PKC compound may be not a pure peptide but instead a peptide-containing compound high in lauric acid derivative.     

Implementation of an interleaved pulse‐width modulation converter for renewable energy conversion

This paper presents an interleaved soft switching converter to achieve the features of zero voltage switching (ZVS) turn‐on for power switches, zero current switching turn‐off for rectifier diodes at full load, less transformer secondary winding with full‐wave diode rectifier topology, and balance primary currents with series connection of the transformer secondary windings. Two circuit modules are adopted in the proposed circuit, and they are operated with an interleaved pulse‐width modulation. Thus, ripple currents at the input and output sides are reduced. In each module, two ZVS converters using the same switches are operated with interleaved half switching cycle. The secondary windings of transformers are connected in series in order to ensure that the primary side currents are balanced. The full‐wave diode rectifier topology is used on the output side such that the voltage stress of rectifier diodes equals output voltage, rather than being two times the output voltage as in a conventional center‐tapped rectifier topology. Laboratory experiments with a 1000‐W prototype are provided to describe the effectiveness of the proposed converter. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrically bistable digital memory behaviors of thin films of polyimides based on conjugated bis(triphenylamine) derivatives

Three functional polyimides (PIs) bearing conjugated bis(triphenylamine) (2TPA) derivatives with electron-donating and accepting groups were synthesized with reasonably high molecular weights. The PIs exhibited high thermal and dimensional stabilities and furthermore produced high-quality nanoscale thin films via conventional solution coating process. All of the PIs in the films were found to be amorphous, but they were oriented somewhat preferentially in the film plane, rather than randomly. Their film densities and interchain distances were measured, and the optical and electrochemical properties were determined. All of the PIs in the devices with aluminum top and bottom electrodes initially revealed a high resistance (OFF-state). However, under positive and negative voltage sweeps, the PIs demonstrated volatile or nonvolatile digital memory behavior, depending on the substituents of the 2TPA unit. The 2TPA-based PI, as well as the PI bearing 2TPA with electron-donating methoxy substituents showed unipolar write-once-read-many-times (WORM) memory behavior, whereas the 2TPA-based PI containing electron-accepting cyano groups exhibited unipolar dynamic random access memory (DRAM) behavior. All of the PI films revealed excellent retention abilities in both the OFF- and ON-state, even under ambient air conditions. Moreover, they all revealed high ON/OFF current ratios (10⁶–10¹⁰). All of the memory behaviors were found to be governed by a mechanism involving trap-limited space-charge limited conduction and local filament formation. Such memory behaviors were further investigated in detail with taking into consideration the PI components' chemical nature and molecular orbital levels, possible trapping sites, substituents' effect, and the metal electrodes' work function. Overall, this study demonstrated that the thermally, dimensionally stable PIs are highly suitable for the low-cost mass production of high performance, polarity-free digital memory devices that can be operated with very low power consumption. Moreover, the memory mode can be tuned by changing the substituent in the 2TPA unit.     

Facile preparation of sago starch esters using full factorial design of experiment

A facile solvent‐free method to acetylate sago starch (Metroxylon sagu) is reported. Microwave (100 W) was used as the heating source and the heating time was varied from 2 to 10 min with the temperature of acetylation maintained at 100°C under continuous stirring. Using a 2⁴ full factorial design of experiment, it was found that the degree of substitution (DS) of acetylated sago starch was strongly affected by the ratio of starch to acylating reagents, the ratio of acetic anhydride to acetic acid as the acylating reagents, the concentration of iodine as catalyst and reaction time. The physicochemical characteristics of the acetylated sago starch were assessed based on the FTIR spectra, the XRD spectra, the water absorption index (WAI), and the water solubility index (WSI). SEM was used to study the surface morphology of the acetylated sago starch at different DS.     

Synergistic effect of aluminum hydroxide and nanoclay on flame retardancy and mechanical properties of EPDM composites

The composites based on ethylene–propylene–diene monomer rubber (EPDM) with aluminum hydroxide (ATH), nanoclay, vulcanizing agent, and curing accelerator were prepared by conventional mill compounding method. The thermal stability and the flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 test, cone calorimeter, and smoke density chamber tests. The results indicated that the substitution of the nanoclay in the EPDM/ATH composites increased the 50% weight loss temperature and the LOI value, and reduced the peak heat release rate (pk‐HRR), the extinction coefficient (Ext Coef), the maximal smoke density (Dm), and the whole smoke at the first 4 min (VOF4) of the test specimens. The synergistic flame retardancy of the nanoclay with ATH in EPDM matrix could imply that the formation of a reinforced char/nanoclay layer during combustion prevents the diffusion of the oxygen and the decomposed organic volatiles in the flame. The mechanical properties of the composites have been increased by replacing more of the nanoclays into the EPDM/ATH blends. The best loading of the nanoclay in EPDM/ATH composites is 3 wt %, which keeps LOI in the enough value, the V‐0 rating in the UL‐94 test, and the improved mechanical properties with better dispersion and exfoliation of the nanoclays shown by transmission electron microscopy (TEM) micrographs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2042–2048, 2013     

Effect of porogenic solvent on the porous properties of polymer monoliths

Polymer monoliths with open pores and median pore size of about 15 nm–3 μm have been successfully synthesized by photoinitiated polymerization of butyl methacrylate and ethylene glycol dimethacrylate monomers. The solubility of the monomers in a porogenic solvent is determined by Hildebrand solubility parameter, and it is found that it has great effect on the pore size of the polymers synthesized. Polymers with larger pores are usually generated with poorer solvents for the monomers. However, polymers with different pore sizes and porosities have been obtained using porogenic solvents with similar Hildebrand solubility parameters. The evaporation rate of the porogenic solvents might be another critical factor affecting the properties of the polymer monoliths. Moreover, the effect of water as a cosolvent on the pore size and porosity of the polymers have also been investigated. Polymers with larger pore size have been prepared with the presence of water due to the occurrence of earlier phase separation in the polymerization. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A practical authentication protocol with anonymity for wireless access networks

The use of anonymous channel tickets was proposed for authentication in wireless environments to provide user anonymity and to probably reduce the overhead of re‐authentications. Recently, Yang et al. proposed a secure and efficient authentication protocol for anonymous channel in wireless systems without employing asymmetric cryptosystems. In this paper, we will show that Yang et al.'s scheme is vulnerable to guessing attacks performed by malicious visited networks, which can easily obtain the secret keys of the users. We propose a new practical authentication scheme not only reserving the merits of Yang et al.'s scheme, but also extending some additional merits including: no verification table in the home network, free of time synchronization between mobile stations and visited networks, and without obsolete anonymous tickets left in visited networks. The proposed scheme is developed based on a secure one‐way hash function and simple operations, a feature which is extremely fit for mobile devices. We provide the soundness of the authentication protocol by using VO logic. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of Modified mRNA in Somatic Reprogramming to Pluripotency and Directed Conversion of Cell Fate

Modified mRNA (modRNA)-based somatic reprogramming is an effective and safe approach that overcomes the genomic mutation risk caused by viral integrative methods. It has improved the disadvantages of conventional mRNA and has better stability and immunogenicity. The modRNA molecules encoding multiple pluripotent factors have been applied successfully in reprogramming somatic cells such as fibroblasts, mesenchymal stem cells, and amniotic fluid stem cells to generate pluripotent stem cells (iPSCs). Moreover, it also can be directly used in the terminal differentiation of stem cells and fibroblasts into functional therapeutic cells, which exhibit great promise in disease modeling, drug screening, cell transplantation therapy, and regenerative medicine. In this review, we summarized the reprogramming applications of modified mRNA in iPSC generation and therapeutic applications of functionally differentiated cells.     

Ultraviolet ZnO Nanorod/P-GaN-Heterostructured Light-Emitting Diodes

Both i-ZnO and n-ZnO : In nanorod arrays were grown on a p-GaN layer with an anodic alumina membrane template using a vapor cooling condensation method. Electroluminescence emissions were observed from the resulting p-n (p-GaN/n-ZnO : In nanorod array) and p-i-n (p-GaN/i-ZnO nanorod array/n-ZnO : In nanorod array) heterostructured light-emitting diodes (LEDs). The ultraviolet emission peak at 386 nm observed in the p-i-n heterostructured LEDs was attributed to radiative recombination of the near-band edge in the i-ZnO nanorods. Using power-law fitted current–voltage relationships, it was shown that a space-charge-limited current and associated effects occurred in the p-n and p-i-n nanorod heterostructured LEDs.      

Interfacial Reactions of Sn-58Bi and Sn-9Zn Lead-Free Solders with Au/Ni/SUS304 Multilayer Substrate

The liquid/solid interfacial reactions of Sn-58Bi (SB) and Sn-9Zn (SZ) lead-free solders with Au/Ni/SUS304 multilayer substrates have been investigated in this study. In the SB/Au/Ni/SUS304 couple, only the Ni₃Sn₄ phase with needle-like grains was formed at the SB/Au/Ni/SUS304 interface. The Ni₅Zn₂₁ phase with a column structure was formed at the SZ/Au/Ni/SUS304 interface. The thickness of both intermetallic compounds (IMCs) increased with increasing reaction temperature and time. Meanwhile, the growth mechanism of these two IMCs is seen to follow a parabolic law and is diffusion controlled.